Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from queue import deque
H, W = map(int, input().split())
matrix = []
count = 0
for i in range(H):
    matrix.append(list(input()))
    count += matrix[-1].count('.')
que = deque([(0, 0, 1)])

visited = set()

while que:
    row, col, depth = que.popleft()

    if not(0 <= row < H and 0 <= col < W) or matrix[row][col] == '#':
        continue
    
    if (row, col) in visited:
        continue

    visited.add((row, col))
    if (row, col) == (H-1, W-1):
        print(count - depth)
        exit()
    
    for ud, lr in ((-1, 0), (1, 0), (0, -1), (0, 1)):
        que.append((row+ud, col+lr, depth+1))
print(-1)